Method for condensation reduction in linear electromechanical actuators

ABSTRACT

A method for reducing condensation includes moving a linear motor slider that is positioned within a housing of an actuator. A first gas is pushed out of a transfer plate chamber through a first vent. A second gas is drawn into the transfer plate chamber through a second vent. Moisture is removed from the second gas as the second gas is being drawn into the transfer chamber by passing the second gas through at least one of a hydrophobic or oleophobic material.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a divisional of U.S. application Ser. No. 14/672,416 filed Mar. 30, 2015 for “METHOD FOR CONDENSATION REDUCTION IN LINEAR ELECTROMECHANICAL ACTUATORS” by D. Balsiger. The present invention relates to electromechanical actuators, and in particular, to a method for reducing moisture in linear electromechanical actuators.

BACKGROUND

The recent trend in modern aircraft is towards developing an all-electric aircraft. Electromechanical Actuators (“EMA”) can be used to fulfill the actuation needs in all-electric aircraft. Since EMAs are electronic devices, EMAs are prone to damage sustained due to moisture. Condensation and seal failure are examples of instances resulting in moisture ingress into an EMA.

SUMMARY

A method for reducing condensation includes moving a linear motor slider that is positioned within a housing of an actuator. A first gas is pushed out of a transfer plate chamber through a first vent. A second gas is drawn into the transfer plate chamber through a second vent. Moisture is removed from the second gas as the second gas is being drawn into the transfer chamber by passing the second gas through at least one of a hydrophobic or oleophobic material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an elevation view of an electromechanical actuator.

FIG. 1B is a cross-sectional view of an electromechanical actuator taken along 1B-1B shown in FIG. 1A.

FIG. 2 is a cross-sectional view of an electromechanical actuator vent taken along 1B-1B shown in FIG. 1A.

DETAILED DESCRIPTION

An EMA's thermal cycle is based on its usage. When an EMA increases in temperature, the air enclosed in the EMA expands putting undesirable load on seals in the EMA. When the temperature in the EMA decreases, the moisture in the air inside of the EMA condenses into water. When the temperature in the EMA decreases below freezing, the water can form into ice, and in extreme cases the ice can fill the air gap within the motor causing failure. One example of procedure currently in use to remove water is to use a drain hole to drain water from the EMA. The drain hole can become plugged or allow foreign material to enter the EMA. Internal heaters are also used in EMAs to keep the moisture laden air above the dew point so that liquid water doesn't form inside the EMAs. While heaters work to keep the liquid from forming, heaters use power and take up valuable weight and space in the EMA.

FIG. 1A is an elevation view of electromechanical actuator 10 a. Electromechanical actuator 10 a includes housing 12 a, aft cover 14 a, forward cover 16 a, and linear motor slider 18 a. Housing 12 a contains a portion of linear motor slider 18 a. The portion of linear motion slider 18 a not contained in housing 12 a includes clevis 20 a. Clevis 20 a is attached to linear motion slider 18 a. Clevis 20 a is configured to engage with a kinetic element (not shown) that connects to electromechanical actuator 10 a. Aft cover 14 a is attached to housing 12 a and is positioned on an aft end of housing 12 a. Forward cover 16 a is attached to housing 12 a and is positioned on a forward end of housing 12 a opposite the aft end of housing 12 a. Airframe mount 22 a is disposed on the aft end of housing 12 a and is formed with aft cover 14 a. Airframe mount 22 a is configured to pivotally mount onto an element of an aircraft. Electromechanical actuator 10 a may include a linear electromechanical actuator or other various types of electromechanical actuators.

Aft vent 24 a and forward vent 26 a are located on housing 12 a. Aft vent 24 a is located near aft cover 14 a. Forward vent 26 a is located between aft vent 24 a and forward cover 16 a. In the present embodiment, both aft vent 24 a and forward vent 26 a are positioned along the same face of housing 12 a. Aft vent 24 a and forward vent 26 a allow entry and exit of a gas from housing 12 a during operation of electromechanical actuator 10 a, as described in more detail below with reference to FIG. 1B.

FIG. 1B is a cross-sectional view of electromechanical actuator 10 b taken along section 2-2. Electromechanical actuator 10 b includes housing 12 b, aft cover 14 b, forward cover 16 b, and linear motor slider 18 b. For clarity, the character reference numerals for the elements of FIG. 1B include the letter “b”, in comparison to the character reference numerals for the elements in FIG. 1A that include the letter “a”. As discussed herein, the character reference numerals used for specific elements with respect to FIGS. 1A and 1B can be used interchangeably, such as for example “housing 12 b” can be used to refer to the same element as “housing 12 a”, and so on and so forth. Housing 12 b contains a portion of linear motor slider 18 b. The portion of linear motion slider 18 b not contained in housing 12 b includes clevis 20 b. Clevis 20 b is attached to linear motion slider 18 b. Clevis 20 b is configured to engage with a kinetic element (not shown) that connects to electromechanical actuator 10 b. Aft cover 14 b is attached to housing 12 b and is positioned on an aft end of housing 12 b. Forward cover 16 b is attached to housing 12 b and is positioned on a forward end of housing 12 b opposite the aft end of housing 12 b. Airframe mount 22 b is disposed on the aft end of housing 12 b and is formed with aft cover 14 b. Airframe mount 22 b is configured to pivotally mount onto an element of an aircraft. Aft vent 24 b and forward vent 26 b are located on housing 12 b.

Housing 12 b also includes transfer plate chamber 28 b. Transfer plate chamber 28 b is divided into two portions by transfer plate 30 b. Transfer plate 30 b divides transfer plate chamber 28 b into transfer plate chamber aft side 32 b and transfer plate chamber forward side 34 b. Aft vent 24 b allows fluid communication between transfer plate chamber aft side 32 b and the outside of housing 12. Forward vent 26 b allows fluid communication between transfer plate chamber forward side 34 b and the outside of housing 12.

Linear motion slider 18 b enters housing 12 b through forward cover 16 b. Seal 36 b is positioned between linear motion slider 18 b and forward cover 16 b. Seal 36 b enables linear motion slider 18 b to slide in and out of housing 12 b while preventing contaminants from entering housing 12 b. Linear motor stators 38 b are located within housing 12 b and circumferentially surround linear motor slider 18 b. Linear motor stators 38 b create a magnetic field which interacts with linear motion slider 18 b causing linear motion slider 18 b to actuate. As linear motion slider 18 b actuates, transfer plate 30 b slides along guide rod 40 b. Guide rod 40 b is positioned within transfer plate chamber 28 b and guides the linear motion of transfer plate 30 b along a linear path of travel. Transfer plate 30 b includes guide rod bushing 42 b which receives guide rod 40 b.

As linear motion slider 18 b moves along housing 12 b, transfer plate 30 b moves in either an aft or forward direction. As transfer plate 30 b moves in an aft direction, gas in transfer plate chamber aft side 32 b will compress and a slight vacuum will be formed in transfer plate chamber forward side 34 b. As gas in transfer plate chamber aft side 32 b compresses, a first gas is pushed out of transfer plate chamber aft side 32 b and through aft vent 24 b. As the slight vacuum is formed in transfer plate chamber forward side 34 b, a second gas is drawn into transfer plate chamber forward side 34 b through forward vent 26 b. Likewise, as transfer plate 30 b moves in a forward direction, gas in transfer plate chamber forward side 34 b will compress and a slight vacuum will be formed in transfer plate chamber aft side 32 b. As gas in transfer plate chamber forward side 34 b compresses, a third gas is pushed out of transfer plate chamber forward side 34 b and through forward vent 26 b. As the slight vacuum is formed in transfer plate chamber aft side 32 b, a fourth gas is drawn into transfer plate chamber aft side 32 b through aft vent 24 b.

Each of aft vent 24 b and forward vent 26 b include either a hydrophobic or oleophobic material. As the second gas is drawn into transfer plate chamber 28 b through either aft vent 24 b or forward vent 26 b, the amount of moisture contaminants such as water, oil, and other fluid contaminants removed from the gas are controlled as the gas enters transfer plate chamber 28 b. A hydrophobic membrane in either aft vent 24 b or forward vent 26 b would control and/or minimize the amount of water moisture from the second gas being drawn into transfer plate chamber 28 b. An oleophobic membrane in either aft vent 24 b or forward vent 26 b would control and/or minimize the amount of oil moisture from the second gas being drawn into transfer plate chamber 28 b. Additionally, aft vent 24 b and forward vent 26 b may remove other types of moisture or liquid contaminants from the gas being drawn into transfer plate chamber 28 b. Aft vent 24 b and forward vent 26 b may also remove various types of particulate contaminants from the second gas being drawn into transfer plate chamber 28 b.

As transfer plate 30 b moves in an aft direction, moist gas will be pushed out of aft vent 24 b and dry gas will be drawn in through forward vent 26 b. As transfer plate 30 b moves in a forward direction, moist gas will be pushed out of forward vent 26 b and dry gas will be drawn in through aft vent 24 b. This action will actively force moisture laden gas out of and draw clean dry air into electromechanical actuator 10 b. Additionally, as electromechanical actuator 10 b heats up, the expansion of the gas inside of transfer plate chamber 28 b will force moisture laden gas out of transfer plate chamber 28 b through either aft vent 24 b or forward vent 26 b. As electromechanical actuator 10 b cools down, the pressure inside transfer plate chamber 28 b will decrease therefore drawing clean dry gas into transfer plate chamber 28 b. The availability of gas to flow through aft vent 24 b and forward vent 26 b allows for air pressure within transfer plate chamber 28 b and air pressure outside of electromechanical actuator 10 b to be in near pressure equilibrium reducing the amount of pressure fatigue experienced by aft vent 24 b and forward vent 26 b.

The active, piston like nature, of electromechanical actuator 10 is used to actively recirculate moisture laden gas with clean dry gas. This recirculation of gas protects the electrical components within electromechanical actuator 10 from condensation.

FIG. 3 is a cross-sectional view of vent 44. Vent 44 is located in a portion of housing 46 and includes membrane 48, spacer plates 50, and vent cover 52. Membrane 48 is positioned fluidly adjacent to transfer plate chamber 54. Spacer plates 50 are positioned between membrane 48 and vent cover 52. Vent cover 52 is positioned at a distal end of vent 44 away from housing 46.

Membrane 48 may include a hydrophobic, oleophobic, or other type of filtering membrane to control transmission of moisture and/or particulate contaminants into transfer plate chamber 54. Membrane 48 is designed to allow one-way passage of contaminants out of transfer plate chamber 54 while minimizing transmission of moisture and/or particulate contaminants into transfer plate chamber 54. An example of membrane 48 can include an oleophobic membrane produced by Gore. An example of the material used for membrane 48 can include polytetrafluoroethylene (ePTFE).

Spacer plates 50 include openings 56. Openings 56 are configured to provide a tortuous flowpath through vent 44. The tortuous flowpath includes a non-linear passage along the flowpath. The tortuous flowpath requires a fluid passing vent 44 to take multiple twists and turns before passing from one end of vent 44 to the other. Specifically, the tortuous flowpath is designed to inhibit a flow of flames through vent 44. This configuration is also applicable to previous embodiments of the present disclosure such that an aft vent may include a first tortuous flowpath and a forward vent may include a second tortuous flowpath. The configuration and/or quantities of spacer plates 50 and openings 56 can be varied to produce desired performance characteristics of vent 44. Vent 44 may also include support plate 58. Support plate 58 is a flat piece of solid material with one or more orifices. Support plate 58 provides membrane 48 with structural support as gas is drawn in and out of transfer plate chamber 54. For example, support plate 58 can support at least one of the at least one of hydrophobic and oleophobic materials (e.g., membrane 48) as the second gas is passed through the at least one of hydrophobic and oleophobic materials.

DISCUSSION OF POSSIBLE EMBODIMENTS

The following are non-exclusive descriptions of possible embodiments of the present disclosure.

An actuator may include a housing. The housing may include a linear motion slider with a portion of the linear motion slider positioned in the housing. A transfer plate may be disposed on an end of the linear motion slider. A transfer plate chamber may be positioned within the housing, wherein the transfer plate may divide the transfer plate chamber into an aft chamber and a forward chamber. An aft vent may be disposed in the aft chamber. The aft vent may include a first membrane positioned over the aft vent. A forward vent may be disposed in the aft chamber. The forward vent may include a second membrane positioned over the forward vent. The first and second membranes may include at least one of hydrophobic and oleophobic materials.

The actuator of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components:

a further embodiment of the foregoing actuator, wherein the actuator may include a linear electromechanical actuator;

a further embodiment of the foregoing actuator, wherein the at least one of hydrophobic and oleophobic materials may control the amount of moisture drawn into the transfer plate chamber;

a further embodiment of the foregoing actuator, wherein the at least one of hydrophobic and oleophobic materials may minimize the amount of moisture drawn into the transfer plate chamber;

a further embodiment of the foregoing actuator, wherein the aft vent may include a first tortuous flowpath and the forward vent includes a second tortuous flowpath;

a further embodiment of the foregoing actuator, wherein the first and second tortuous flowpaths may inhibit the flow of flames through the aft vent and the forward vent respectively; and

a further embodiment of the foregoing actuator, wherein the at least one of hydrophobic and oleophobic materials may minimize an amount of particulate contaminants from entering the transfer plate chamber.

A method for reducing condensation may include moving a linear motion slider of an actuator. The linear motion slider may be positioned within a housing of the actuator. A first gas may be pushed out of a transfer plate chamber through a first vent. A second gas may be drawn into the transfer plate chamber through a second vent. Moisture may be removed from the second gas as the second gas is being drawn into the transfer plate chamber by passing the second gas through at least one of hydrophobic and oleophobic materials.

The method for reducing condensation of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components:

a further embodiment of the foregoing method for reducing condensation, wherein the method may further include actuating a linear electromechanical actuator;

a further embodiment of the foregoing method for reducing condensation, wherein the amount of moisture drawn into the transfer plate chamber with the at least one of hydrophobic and oleophobic materials may be controlled;

a further embodiment of the foregoing method for reducing condensation, wherein the amount of moisture drawn into the transfer plate chamber with the at least one of hydrophobic and oleophobic materials may be minimized;

a further embodiment of the foregoing method for reducing condensation, wherein drawing the second gas into the transfer plate chamber may include drawing the second gas through a tortuous flowpath;

a further embodiment of the foregoing method for reducing condensation, wherein a flow of flames through a first tortuous flowpath in the first vent or through a second tortuous flowpath in the second vent may be inhibited; and

a further embodiment of the foregoing method for reducing condensation, wherein an amount of particulate contaminants from entering the transfer plate chamber may be minimized.

While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims. 

The invention claimed is:
 1. A method for reducing condensation, the method comprising: activating a linear electromechanical actuator by moving a linear motor slider of the linear electromechanical actuator, wherein the linear motor slider is positioned within a housing of the linear electromechanical actuator; pushing a first gas out of a first transfer plate chamber through a first vent including a first tortuous flowpath; drawing a second gas into a second transfer plate chamber through a second vent, wherein drawing the second gas into the second transfer plate chamber includes drawing the second gas through a second tortuous flowpath; removing moisture from the second gas as the second gas is being drawn into the second transfer plate chamber by passing the second gas through at least one of hydrophobic and oleophobic materials; and inhibiting a flow of flames through the first tortuous flowpath in the first vent or through the second tortuous flowpath in the second vent.
 2. The method for reducing condensation of claim 1, the method further including controlling the amount of moisture drawn into the second transfer plate chamber with the at least one of hydrophobic and oleophobic materials.
 3. The method for reducing condensation of claim 2, the method further including minimizing the amount of moisture drawn into the second transfer plate chamber with the at least one of hydrophobic and oleophobic materials.
 4. The method for reducing condensation of claim 1, the method further including minimizing an amount of particulate contaminants from entering the first and second transfer plate chambers.
 5. The method for reducing condensation of claim 1 further comprising forcing the first gas out of the linear electromechanical actuator.
 6. The method for reducing condensation of claim 1 further comprising drawing dry air into the linear electromechanical actuator.
 7. The method for reducing condensation of claim 1 further comprising recirculating a moisture laden gas with a clean dry gas.
 8. The method for reducing condensation of claim 1 further comprising supporting at least one of the at least one of hydrophobic and oleophobic materials with a support plate as the second gas is passed through the at least one of hydrophobic and oleophobic materials.
 9. The method for reducing condensation of claim 1, wherein moving the linear motor slider comprises creating a magnetic field with a linear motor stator, wherein the magnetic field interacts with the linear motion slider causing the linear motion slider to actuate.
 10. A method for reducing condensation, the method comprising: moving a linear motor slider of a linear electromechanical actuator, wherein the linear electromechanical actuator comprises: a housing; a portion of the linear motor slider positioned in the housing; a transfer plate disposed on an end of the linear motor slider; a transfer plate chamber positioned within the housing, wherein the transfer plate divides the transfer plate chamber into an aft chamber and a forward chamber; an aft vent disposed in the aft chamber, wherein the aft vent includes a first membrane positioned over the aft vent; and a forward vent disposed in the forward chamber, wherein the forward vent includes a second membrane positioned over the forward vent; pushing a first gas out of the aft chamber through the aft vent; drawing a second gas into the forward chamber through the forward vent; and removing moisture from the second gas as the second gas is being drawn into the forward chamber by passing the second gas through the second membrane.
 11. The method of claim 10, wherein the first and second membranes include at least one of hydrophobic and oleophobic materials.
 12. The method for reducing condensation of claim 10 further comprising actuating the linear electromechanical actuator.
 13. The method for reducing condensation of claim 12 further comprising controlling the amount of moisture drawn into the forward chamber with at least one of the first and second membranes.
 14. The method for reducing condensation of claim 13, further comprising minimizing the amount of moisture drawn into the forward chamber with the at least one of the first and second membranes.
 15. The method for reducing condensation of claim 10, wherein drawing the second gas into the forward chamber includes drawing the second gas through a tortuous flowpath.
 16. The method for reducing condensation of claim 10, further comprising inhibiting a flow of flames through a first tortuous flowpath in the first vent or through a second tortuous flowpath in the second vent.
 17. The method for reducing condensation of claim 10, further comprising minimizing an amount of particulate contaminants from entering the transfer plate chamber. 